Photoelectric cell



PHOTOELECTRIG CELL Filed July 2i, 1957 Light senfsz've lager INVENTOR.

/z/'S 4 ATTORNEY.

Patented Dec. 12, 1939 UNITED STATES PATENT OFFICE PHOTOELECTRIO CELLKurt Gabler, Dresden, Germany, assigner to Zeissv IkonAktiengesellschaft, Dresden, Germany Application July 21, 1937, SerialNo. 154,725 In Germany November 30, 1936 2 Claims. (Cl. 13S- 89) Theinvention relates to improvements in outer surface of the lightsensitive layer 2 and photoelectric cells, and particularly pertains tothen an intermediate protective layer 4 is photoelectric cells employedin exposure meters. arranged upon the lacquer coating 3. The lac-Photoelectric cells, for instance cuprous oxide quer may consist of astyrol product which asis 5 or selenium cells change their sensitivenesswhen Well known is very adhesive. 5 subjected to atmospheric influences.It is there- The intermediate protective layer 4 consists forenecessary, especially in tropical climates, to preferably of hydratedcellulose of a type which protect the photoelectric cell against adverseatdoes not readily combine with the lacquer coatmospheric conditions, inorder to prevent faulty ing 3. Such types of hydrated cellulose are formeasurements of the exposure time when using a example Cellophane. 10photoelectric exposure meter. It is customary, Upon the intermediatelayer 4 is then applied to apply a coat of lacquer to the surface of thea cover layer 5 which preferably extends around photoelectric cell, butfor tropical climates such, the edges of the photoelectric cell asindicated coat of lacquer does not afford suiiicient protec- 'at 6 andthen iS folded aft 1 inwardly against the tion. bottom surface of thebase member I. The cover 15 It is not the principal object of theinvention layer 5 consists preferably a synthetic resin, for to providea photoelectric cell with means conexample a foil consisting of resin ofplexicum (a stituting a sufficient and durable protection derivativefrom acrylic acid).

against adverse climatical condition encountered The conductor terminalsBand 9 are applied especially in the tropics. to the cell in customarymanner.

I am aware of the fact, that it has been pro- Obviously, the lacquercoating 3, the interposed heretofore to protect photoelectric cellsmediate layer 4 and the cover layer 5 have to whose surface is providedwith a. lacquer coating be transparent to admit adequately the lightrays by an additional coating which is vapor and to the light sensitivelayer 2. moistureproof and which consists of a thin foil What I claim asmy invention is:

of some suitable material as for instance some l. A photoelectric cellcomprising a base memsynthetic resins. Such additional coating, hoW- berprovided with a light sensitive layer having ever, has proven not verysatisfactory, because applied on its outer surface a coating of lacquer,the sensitiveness of the photoelectric cell was unand means forprotecting said light sensitive favorably influenced thereby. It appearsthat layer against tropical atmospheric conditions, 30 this undesirablecondition is due to the fact that said means consisting of a layer ofhydrated such foils merge into the lacquer coatlngon the cellulosearranged on top of said lacquer coating surface of the cell. As thelacquer layer has and a cover layer of transparent synthetic resinanother coelcient of expansion than the foil a applied on top of saidcellulose layer, said syndecreasing or increasing of temperature willprothetic resin layer extending around the edges of 35 `duce internalstresses and hereby damage the the superimposed assembly of said basemember, photoelectric layer. light sensitive layer, lacquer coating andcellu- It is therefore another object of the invention lose layer. toprovide the photoelectric cell which has a 2. A photoelectric cellcomprising a base mem- 40 lacquer coating with a protective layer whichber provided with a light sensitive layer having will not influence thesensitiveness of the cell applied on its outer surface a coating oflacand which will not combine or will not merge quer,land means forprotecting said light sensiappreciably with the said surface coating ofthe tive layer against tropical atmospheric condiphotoelectric cell.Thereupon a layer which tions, said means consisting of a layer ofhyforms the real protection against detrimental drated cellulosearranged on top of said lacquer 45 atmospheric influences is applied ontop of this coating and a cover layer of transparent synintermediate orauxiliary protective layer. thetic resin applied on top of saidcellulose layer, The drawing shows by way of example a crosssaidsynthetic resin layer extending around the sectional view of aphotoelectric cell of the presedges of the superimposed assembly of saidbase ent invention greatly magniiled. member, light sensitive layer,lacquer coating and `'I'he photoelectric cell consists of a basememcellulose layer, and being folded with its marginal ber I upon whichthe light sensitive layer 2 conportion against the underside of saidbase memsisting for example o! cuprous oxide or selenium ber. isarranged. A coat 3 of lacquer is applied to the KURT GBLER.

